Hello,
Maybe Internet Explorer 7 don't support outlook anymore, why are you still on IE 7 ? Try to upgrade it or use any another browser.
This is common problem, outlook usually don't works in old version of browsers, I did test it on old version of Opera and found same result. You had better upgrade your browser or try any another.
Or check this http://support.microsoft.com/kb/310049 , maybe it will help you.
Regards,
Fahadking07